Chapter 11 Muscular Tissue Flashcards
1
Q
Skeletal muscle tissue
A
Locations: combined with connective and nervous tissue in skeletal muscle
Functions: moves or stabilizes the position of the skeleton
2
Q
Cardiac muscle tissue
A
Location: heart
Functions: circulates blood, maintains blood pressure
3
Q
Smooth muscle tissue
A
Locations: walls of blood vessels, digestive system, respiratory, urinary and reproductive organs
Functions: moves food, urine, reproductive secretions, regulates diameter of blood vessels
4
Q
Excitablity
A
Responsiveness to chemical signals, stretch and electrical changes across the plasma membrane
5
Q
Conductivity
A
Local electrical excitation sets off a wave of excitation that travels along muscle fiber
6
Q
Contractility
A
Shortens when stimulated
7
Q
Extensibility
A
Capable of being stretched between contractions
8
Q
Elasticity
A
Returns to its original length after being stretched
9
Q
Skeletal muscle
A
Voluntary striated muscle usually attached to bones
10
Q
Striations
A
Altering light and dark transverse bands
11
Q
Voluntary
A
Subject to conscious control
12
Q
Endomysium
A
Connective tissue around muscle cell
13
Q
Perimysium
A
Connective tissue around muscle fascicle
14
Q
Epimysium
A
Connective tissue surrounding entire muscle
15
Q
Sarcolemma
A
Plasma membrane of a muscle fiber
16
Q
Sacroplasm
A
Cytoplasm of a muscle fiber
17
Q
Myofibris
A
Long protein cords occupying most of sarcoplasm
18
Q
Glycogen
A
Carbohydrate stored to provide energy for exercise
19
Q
Myogoblin
A
Red pigment
Provides some oxygen needed for muscle activity
20
Q
Multiple nuclei
A
Flattened nuclei pressed against the inside of the sarcolemma
21
Q
Myoblasts
A
Stem cells that fused to form each muscle fiber early in development
22
Q
Satellite cells
A
Unspecialized myoblasts remaining between muscle fiber and Endomysium
23
Q
Where’s mitochondria in muscle fiber
A
Packed into spaces between myofibrils
24
Q
Sarcoplasmic reticulum
A
Smooth ER that forms a network around each myofibril
25
Terminal cisterns
Dilated end-sacs of SR which cross the muscle fiber from one side to the other
26
T tubules
Tubular unfolding of the sarcoldmma which penetrate through the cell and emerge on the other side of
27
Triad
a T tubule and two terminal cisterns associated with it
28
Thick filaments
Made of several hundred myosin molecules
29
Thin filaments
Fibrous actin
Tropomyosin molecules
G actin
Troponin molecule
30
Elastic filaments
Titin
Runs through core of thick filament and anchor it to Z disc and M line
Provides overstretching
Helps position thick filament
31
Purpose of sarcoplasmic reticulum
-contains pumps moving calcium from sarcoplasm to SR
-calcium is essential and critical for muscle contraction
32
Contractile proteins
Myosin and actin do the work of contraction
33
Regulatory proteins
Tropomyosin and tropnin
-acts as switch determining when fiber can or cannot contract
34
Dystrophin
Important protein
-transfers forces or muscle contraction to tendon
35
A Band
Dark, anisotropic
-darkest part where thick filaments overlap the thin filaments
36
H Band
Middle of A band
-thick filaments only
37
M Line
Middle of H band
38
I Band
Light, isotopic
39
Z disc
Provides anchoring for thin filaments and elastic filaments
40
Sarcomere
From Z disc to Z disc
41
Why do muscle cells shorten
Because their individual sarcomeres shorten
42
Do thick or thin filaments change length during shortening
No, neither do
43
Sliding filaments theory
1. H bands and I bands overlap
2. Zones overlap and get larger
3. Z lines approach each other
4. A band remains constant
44
Describe a muscle
-A contractile organ
-attached to bones by tendons
-composed of fascicles of muscle fibers
-supplied with nerves and blood vessels
45
Describe a fascicle
-Bundle of muscle fibers within a muscle
-supplied by nerves and blood vessels
-enclosed in fibrous Perimysium
46
Describe a muscle fiber
-single muscle cell
-slender elongated thread like
-enclosed in its sarcolemma
-contains myofilements and proteins for contracting muscles
47
Describe a Myofibril
-bundle of myofilaments within a muscle cell
-surrounded by SR and mitochondria
-fills cytoplasm
48
Describe a Sacromere
-One Z disc to the other I. Organized patter
-hundreds of sacromeres make up one myofibril
49
Describe Myofilements
Protein strands that carry out the contraction process
Thick: composed mainly on myosin
Thin: composed mainly of actin
50
Motor unit
-One nerve fiber and all the muscle fibers innervated by it
-dispersed throughout muscle
-produces weak contraction over wide area
-effective contraction requires several motor units at once
51
Small motor units
-fine degree of control
- 3-6 muscle fibers per neuron
-eye and hand muscles
52
Large motor units
-more strength than control
-powerful contractions supplied by large motor units with hundrends of fibers
53
Somatic motor neurons
-nerve cells whose cell bodies are in the brain stem and spinal cord that serve skeletal muscles
-each nerve fiber branches out to multiple muscle fibers
-each muscle fiber is supplied by only 1 motor neuron
54
Synapse
Point where a nerve fiber meets its target cell
55
Neuromuscular junction
When target cell is a muscle fiber
56
Axon terminal
Swollen end of nerve fiber
-contains acetylcholine
57
Synaptic cleft
Gab between axon terminal and sarcolemma
58
How many NMJ per muscle fiber
1
59
What does nerve impulse cause
Causes synaptic cleft vesicles to undergo exocytosis releasing ACh into synaptic cleft
60
Basal lamina
Thin layer of collagen and glycoprotein separating Schwann cell and muscle cell from surrounding tissue
-contains AChE which breaks down ACh
61
Schwann cell
Envelopes and isolates NMJ
62
NMJ consists of
1, synaptic terminal of neuron
2, motor end plate
3, synaptic cleft
63
Voltage
A difference in electrical charge
64
Resting potential
-90mV
65
In a unstimulated cell:
-more negative ions inside membrane
-membrane is charged with negative resting potential
-excess sodium ions in ECF
-excess potassium ions in ICF
66
In stimulated cell:
-na gates open
-na flows into cell
-positive inside
67
Depolarization
Inside plasma membrane becomes positive
68
Repolarization
Plasma membrane becomes negative again
69
Impulse
Wave of excitation from cells
70
Spastic paralysis
A state of continual contraction of the muscles
71
Tetanus
Lock jaw
Form of spastic paralysis
72
Flaccid paralysis
Muscles are limp and can’t contract
73
Curare
Competes with ACh for receptor sites but does not stimulate muscles
74
Botulism
Type of food poisoning blocking release of ACh
75
Myasthenia gravis
Loss of ACh receptors at NMJ
76
Rigor mortis
Post mortem ATP production stops and membranes become leaky
-CA2+ leaks out of SR setting muscle contraction cycle in motion
-CA2+ activates myosin actin bridges
-No ATP for bridges
-lysosomes digest bridges
-hardening of muscles and stiffening of body after death
77
Excitation contracting coupling
Events that link the action potentials on the sarcolemma activation of the myofilements,
Preparing them to contract
78
Contraction
Step in which muscle fiber develops tension and may shorten
79
Relaxation
When stimulus ends, muscle fiber relaxes and returns to resting length
80
Excitation
Nerve action potentials lead to muscle action potentials
81
Activities at the neuromuscular junction
1. Action potential at synaptic terminal causes exocytosis of ACh
2.ACh diffuses across synaptic cleft and binds to receptors causing release of Na+
3. Sarcolemma generates action potential and AChE inactivates receptors
82
Muscle fiber contraction cycle
1. Arrival of calcium
2. Calcium binds to troponin
3. Cross bridge formation
4. Stored energy in myosin head releases and gos towards M line
5. Cross bridge detachment
6. Myosin reactivation
83
Length tension relationship
Amount of tension generated by a muscle depends on how stretched or shortened it was before it was stimulated
84
Threshold
Minimum voltage necessary to generate an action potential in muscle fiber and produce a contraction
85
Twitch
Quick cycle of contraction and relaxation when stimulus is at threshold or higher
86
Latent period
Brief delay between stimulus and contraction
87
Isometric muscle contraction
-muscle produces internal tension but external resistance
-stays the same length
88
Isotonic muscle contraction
Muscle changes in length with no change in tension
89
Immediate energy source
-short, intense activities
-myogoblin provides brief supply of oxygen
-phosphagen system utilizes creatine to regenerate ATP providing energy for around 6 seconds of high intensity exercise
90
Short term energy source
-muscles switch to anaerobic fermentation
-converts glucose to lactate for ATP production for 30-40 seconds
91
Long term energy source
-Relies on aerobic respiration providing ATP
-utilizing glucose and fatty acids
92
Muscle fatigue
Progressive weakness due to prolonged activity
Impairs muscle function
93
VO2 Max
-indicates maximum rate of oxygen consumption during intense exercise
-proportional to body size, peaks at age 20
-declines 15% per decade without active aerobic engagement
94
Excess post exercise oxygen consumption
-increased rate of oxygen intake following activity
-essential for recovery
95
Fast twitch fiber (type II)
-quick powerful bursts of energy
-thick and strong
-responsible for rapid movements
-rely on anaerobic metabolism
96
Slow twitch fibers (type I)
-adapted for endurance activities to resist fatigue
-maintains posture
-high density mitochondria, myoglobin and capillaries giving red appearance
97
Intermediate fibers (type IIA)
-exhibit both fast and slow twitch fibers
-provides balance for endurance and power
-common in animals more than humans
98
Muscular dystrophy
-muscle degeneration replaced with fat and scar tissue
-hereditary
-caused by mutation in dystrophin gene
99
Myasthenia gravis
-antibodies attack neuromuscular junctions
